Local-scale controls of a low-severity fire regime (1750–1950), southern British Columbia, Canada

Abstract

Historical low-severity fire regimes are well characterized in ponderosa pine and mixed-conifer forests at many sites in the western United States, but not in the southern interior of British Columbia, Canada. We reconstructed a history of low-severity fires (1750–1950) near the northern limit of ponderosa pine and demonstrated that local-scale spatial variation in fire frequency varied with topography and that the intra-ring position of fire scars (a proxy for fire seasonality) varied somewhat with topography but more strongly by tree species. Fires were significantly more frequent on the south than the north aspect (14 versus 24 y mean plot fire intervals, respectively), likely due to differences in fuel type and condition. Frequency did not vary with elevation, although our range of elevation is likely too narrow to detect such variation (227 m). Ring-boundary scars were 5.6 times more likely on Douglas-fir than ponderosa pine, 1.8 times more likely on north than south aspects, and 1.6 times more likely at low than high elevation. Our results confirm the importance of understanding the effect of interspecific variation and topography on cambial phenology and hence intra-ring position before inferring historical fire seasonality from fire scars.